Discrepant luminosity classes derived for the same → Am star
when different criteria are used. Lore specifically, a luminosity criterion may
indicate a → giant star,
wheras another criterion indicates a → supergiant.

The splitting of a spectral line into several components
in the → Zeeman effect when the magnetic field is weak.
The splitting is much more complex than in the normal effect. The number of
components of the lines often considerably exceeds their number in the normal effect.
Contrarily to the normal Zeeman effect, the anomalous effect
cannot be explained by classical theory. The historically "anomalous" effect is
accounted for by the inclusion of electron spin in the total angular moment.
In fact the idea of electron spin was put forward (Uhlenbeck and Goudsmit, 1926)
to explain the anomalous Zeeman effect.

A long term, generally irregular modulation of → light curves
of a large subclass of → RR Lyrae stars.
Most of the modulations occur on the time scale of some 60 periods, although the
range extends from some tens to some hundreds of periods. Since its discovery
over a hundred years ago, a number of explanations have been proposed for this
effect, but its nature is still a matter of investigation.
The explanations include: closely spaced pulsation modes,
a modal 1 : 2 resonance, an oblique rotator model, a non-radial modal
interaction, convective cycles, and nonlinear resonant
mode coupling between the 9th overtone and the fundamental mode (see, e.g.,
R. Buchler and Z. Kolláth 2011, astro-ph/1101.1502).

A small attractive force that appears between two close parallel
uncharged plates in a vacuum. It is due to quantum vacuum fluctuations
of the electromagnetic field. According to the quantum theory, the
vacuum contains → virtual particles which are
in a continuous state of
fluctuation. Because the distance between the plates is very small,
not every possible wavelength can exist in the space between the two plates,
quite in contrast to the surrounding vacuum. The energy density
decreases as the plates are moved closer, creating a negative pressure which pulls the
plates together. The first successfully measurement of the effect was by Steve Lamoreaux
in 1997. A more recent experiment in 2002 used a polystyrene sphere 200 μm in diameter
coated in gold or aluminium. This was brought to within 0.1 μm of a
flat disk coated with the same metals. The resulting attraction between them
was monitored by the deviation
of a laser beam. The Casimir force was measured to within 1% of the expected
theoretical value.

After the Dutch physicist Hendrik Casimir (1909-2000), who predicted the phenomenon in 1948;
→ effect.

From a hydrodynamical model first proposed by Guillermo Tenorio-Tagle
(1979).
Champagne,
Fr., short for vin de Champagne "wine from Champagne,"
a historical region at northeast France,
from L.L. campania "flat open country," from L. campus
"field;" → effect.

The apparent → deflection of a body in motion with
respect to the Earth, as seen by an → observer
on the Earth, caused by the
→ Earth's rotation. Thus, a projectile fired due north from
any point on the northern hemisphere will land slightly east of its target
(deflection to the right). This involves two factors: 1) the eastward velocity of
Earth's surface decreases from the → equator
to the → poles, and 2)
when an object starts to move north or south without being firmly connected to
the ground it maintains its initial eastward speed
(conservation of → angular momentum).
Hence, an object travelling away from the equator will be
heading east faster than the ground and will seem to be forced east.
On the other hand, a ball fired in the northern hemisphere
toward the equator deflects to the west. As for the southern hemisphere, a ball
fired southward will deflect East.
The projectile is not subject to this effect
only on the equator, when it is thrown in an east-west direction.
The Coriolis effect is therefore greater at higher → latitudes
and smaller near the
equator.
This effect is of paramount importance to the large-scale
→ atmospheric circulation, the development of storms, and the
sea-breeze circulation.
In low pressure systems, i.e. zones where air ascends, the air is less
dense than its surroundings and this creates a center of low
atmospheric pressure. Winds blow from areas of
high pressure to areas of low pressure, and so the surface winds would
tend to blow toward a low pressure center. But, because of the
Coriolis effect, they are deflected. In the northern
hemisphere they are deflected toward the right, and fail to arrive
at the low pressure center, but instead circulate around it
→ counterclockwise. In the southern hemisphere
the circulation around a low pressure center would be
→ clockwise.
Regarding high pressure systems in the northern hemisphere, a general clockwise
rotation is created around the center.
Same as the → Coriolis force. See also
→ geostrophic wind, → geostrophic flow.

Named after Gaspard Gustave Coriolis (1792-1843), French engineer and mathematician
who first described this effect; → effect.

diamond ring effect

اسکر ِ انگشتر ِ الماس

oskar-e angoštar-e almâs

Fr.: effet anneau de diamant

An intense flash of light that happens a few seconds before and after
totality during a solar eclipse. The effect is caused by the last rays
of sunlight before totality (or the first rays of sunlight after totality)
shining through valleys on the edge of the Moon.

Change in frequency of a wave (light, sound) due to the relative
motion of source and receiver. Approaching objects have their
wavelengths shortened. Receding objects have emitted wavelengths
lengthened.

Doppler, after Christian Andreas Doppler (1803-1853), Austrian physicist
who first described how the observed frequency of sound and light waves is affected by
the relative motion of the source and the detector;
→ effect.

dynamo effect

اسکر ِ دینامو

oskar-e dinâmo

Fr.: effet dynamo

The generation of magnetic fields by movements within a
→ plasma, such
as the → convective cores and
→ convective envelopes of stars. The magnetic field is
intensified by the motion of the plasma in much the same way as in a dynamo.
The generated magnetic field is not static, but evolves over time.

In a → rotating star, the sum of the
→ gravity and the → centrifugal
acceleration. The effective gravity is a function of the rotation velocity
(Ω) and the → colatitude (θ).
At the pole (θ = 0°) and the equator (θ = 90°) the effective
gravity is radial.
See also → total gravity.